Pavement for roads, parking lots, airport runways, and so forth is generally of two types, rigid or flexible. Rigid pavement is formed principally of cement, whether natural or manufactured such as portland cement, crushed stone, sand and water for hydration. Flexible pavement on the other hand is formed principally of asphaltic or bituminous materials with aggregate. Flexible pavement is notably less expensive than rigid pavement but its useful life is much shorter and its load bearing ability is measurably less.
It is a principal purpose of the present invention to improve upon rigid pavement so as to achieve substantial reduction in material volume and yet preserve its superior load bearing ability. The object is to make strong durable rigid pavement cost competitive with less expensive flexible pavement.
The crux of the invention achieving these goals is the creation of voids within rigid pavement. The concept is not applicable to flexible pavement because asphaltic and bituminous materials are inherently too weak to permit such voids. Also, flexible pavement materials tend to creep during use over time and this would result in deformation and even crushing of any voids within the pavement structure.
Major runways, taxiways and aprons are seldom made of flexible pavement because their useful life is too short and they are unable to withstand the high loading imposed from heavy commercial or military aircraft use at reasonable cost. The main objectives of the present invention described above, namely reduction of pavement material volume while maintaining high load resistance, are particularly applicable to airport runways, taxiways and aprons.
Formation of voids within roadway surfacing material is not in itself novel. U.S. Pat. Nos. 4,801,217, 4,815,963 and 4,850,738 are examples disclosing roadway materials formed with voids, for example an underlayment for roads built over swampy or unstable ground. However, none of those references concerns rigid concrete pavement. Forms of various types which are used to create cellular slabs permitting water drainage are also well known, such as those described in U.S. Pat. Nos. 4,574,541 and 5,030,343. Again, however, prior art drainage panels and cells such as these do not concern rigid pavement.